speciation/ formation of new species and chapter 19 and start of 20

speciation

formation of 2 new species from 1 species

allopatric speciation

when natural geographic situations prevent gene flow by isolating populations and 2 new species develop.

dispersal allopatric speciation

when few members of species move to a new area

variance speciation

natural situation arises to physically divide organisms.

ex formation of new river.

adaptive radiation

when organisms diversify rapidly from ancestral species, multiple speciation events occur.

ex. darwin’s finches beaks.

sympatric speciation

speciation event without a geological difference

occurs when cells separate and have too many or too few chromosomes in a condition called aneuploidy.

aneuploidy

when chromosome pairs separate and the end cell product has too many or too few individual chromosomes

polyploidy

condition when cells have extra set or sets of chromosomes

autopolyploidy

condition when a polyploid individual will have two or more complete sets of chromosomes from its own species. interbreed

allopolyploid

another form of polyploidy occurs when individuals of two different species reproduce to form a viable offspring

hybrid zone

an area where two closely related species continue to interact and reproduce, forming hybrid

reinforcement

hybrids are less fit than the parents, ___ and the species continue to diverge until they can no longer mate and produce viable offspring

fusion

reproductive barriers weaken until 2 different species becomes 1

stability

fit hybrids continue to become one.

gradual speciation

species diverge gradually through time wish small steps

punctuated equilibrium

species exhibit a large change in a short period and then remain unchanged for a long period

allele frequency/gene frequency

is the rate at which a specific allele appears within a population

founder effect

an event that initiates an allele frequency change in an isolated part of the population, which is not typical of the original population

hardy-weinberg

when/if a LARGE population reproduces sexually at random, then the genetic frequencies should not change in next generation (remains in equilibrium)

genetic drift

effect of chance, By chance, some individuals will have more offspring than others

small populations more susceptible

reduces genetic variability,

selection pressure

driving selective force, were the only one acting on the population

bottleneck effect

results in suddenly wiping out a large portion of the genome. survivors' genetic structure becomes the entire population's genetic structure, which may be very different from the pre-disaster population.

gene flow

: the flow of alleles in and out of a population due to the migration of individuals or gametes

sexual dimorphisms

where there is more variance in the male's reproductive success than that of the females

intrasexual selection

individuals of one sex compete directly for mates of the opposite sex

Intersexual selection

individuals of one sex (usually the females) are choosy in selecting their mates from the other
sex.

rooted phylogenetic tree

single lineage (at base) represents common
ancestor

unrooted phylogenetic tree

shows relationships but not the common ancestor. (like a circle)

root

indicates that an ancestral lineage gave rise to all organisms of the tree

branch point

indicates where 2 lineages diverged

basal taxon

lineage that evolved early and remains unbranched.

sister taxa

when 2 lineages stem from the same branch point

polytomy

branch with more than 2 polytomy

taxon

taxons that share more recent common ancestors are more closely related.

clade

a grouping that includes a common ancestor
and all the descendants (living and extinct) of that
ancestor (monophyletic groups

monophyletic group

consists of an ancestral species and all of its descendants

paraphyletic group

consists of an ancestral species and some but not all of its descendants

polyphyletic group

includes distantly related species but does not include their most recent common ancestor.

directional selection

certain trait in a population becomes more or less common over time because individuals with extreme forms of that trait have a higher chance of surviving and reproducing.

diversifying selection

when 2 or more distinct phenotypes each have their advantages for natural selection. results in increasing variance.

stabilizing selection

where individuals with intermediate or average traits have higher fitness compared to those with extreme traits. This leads to a reduction in the variation of a trait within a population over time.

frequency-dependent selection

Frequency-dependent selection is a concept in biology where the fitness of a trait (how well it helps an organism survive and reproduce) depends on its frequency in the population. In other words, the success of a particular trait can change based on how common or rare it is among individuals in a population.

ex. right and left mouth fish